Crude's losses accelerated, erasing gains sparked by OPEC's November output agreement, as concerns over a supply glut mounted. U.S. stocks fluctuated after falling in oil's low as earnings boosted insurers.

West Texas Intermediate crude fell more than 4 percent, plunging below $46 a barrel for the first time since November. The S&P 500 Index was virtually unchanged after sliding in midday trading, as American International Group Inc. led gains among insurers. Metals extended their biggest daily plunge of the year amid ample supplies and concern demand from China is flagging. Treasury yields headed higher after the Federal Reserve signaled it's on track to lift rates in June.

The price surge sparked by OPEC's November deal to curb output has been wiped out as signs of a global supply glut emerged, adding to a recent rout in commodities from copper to iron ore.